Electron discharge tube



April 30, 1935. G. J. LAMBERT; ET A v 1,999,465

ELECTRON DISCHARGE TUBE Filed July 29, 1952 ml lmlhmmll Ilia INVENTORS G.J. LAMBERT JM. NEYJES ATTQR NEY I 1,999,4 PATENT OFFICE 1,999,465 ELECTRON, nrscmmcs TUBE Gregor-ins Johan Lambert; Eindhoven,

and

Johannes Willem Meyjes, Nymegen, Nether- I lands, assignors to Radio Corporation of America, a corporation of Delaware Application July 29, 1932, Serial No. 625,846 In the Netherlands August 4, 1931 5 Claims. (01. 250-275) This invention relates to electron discharge tubes, and more particularly to the manner of mounting the electrodes in such tubes.

It is one of the objects oi the present invention 5 to arrange the conductive parts within the tube in such a manner with respect to one another that perfect insulation between the said parts is obtained while at the same time resulting in a simple construction. I s

It is known that glass beads are generally used in electron discharge tubes in which the supporting and supply conductors of the different electrodes are frequently fixed together by means of such beads. Applicants have found howevenxthat the use thereof entails several drawbacks. For example, when these beads are used, the distances between the conductive parts flxeditherein are often too small due to which short circuits may occur between said parts especially at high temperatures. These short circuits may also result from conductive material depositing on the surface of the insulating body, which'may bring about an electric connection between the parts fixed to the insulating body. Moreover, dlfiiculties' are sometimes encountered on account of stress set up in such bodies by expansion oi'the parts secured thereto. The present invention has for its purpose to avoid the drawbacksinherent in the use oi such insulating beads. In an flectron discharge tube according to the invention two or more electrically conductive parts are connected together by means of a body consisting of insulatingmaterial which is mounted in the tube independentlyof the wall thereof and providedwith one or more recesses. In one or more of the recesses a conductive part may be fixed, whilst said recesses may also be provided between the conductive parts fixed in the body. It has been found that I a verysuitable construction is obtained by constituting the body by two or more coaxial or substantially coaxial tubes, the conductive part being provided in the inner tube whereas another con; ductive part is fixed to the outer tube. Excellent results may be obtained it the conductive. pert provided in the inner tube is movable in a-longitudi'nal direction within this tube. Furthermore a suitable construction is obtained by securing to the outer tube one of the conductive parts in 7 form of or by meansof a clasp surrounding this tube or by providing that the part attached to this outer tube is partly sunk therein. By means of the constructions according to the invention the drawbacks referredto in the pre amble may be avoided for the greater part since the so-called leakage path between the dlflerent conductive parts may be made much longer than that frequently obtained with the usual beads. Moreover, short circuits occurring between said parts over the surface or the body due to deposits of conductive material may be entirely avoided. Moreover the constructions referred to above permit the conductive parts to expand freely without stress being produced in the bodies consisting of insulating material. I

Said bodies may also consist with advantage of two or more coaxial insulating tubeswhich are connected together at one of the ends and closed v at this end. However, they may also be constituted by two coaxial insulating tubes fixed together in the middle or about in the middle. Furthermore, there are several manners of securing the conductive parts in and to said bodies. One of said parts may be taken, for instance, through the inner tube, whereas another conductive part is attached to the outer side of the outer tube. Moreov'enit is also possible to secure on either side of an insulator formed in this way a conductive part in the inner tube and a third conductive part to the outer side of the outer tube.

In order to improve the insulation in the latter case the inner tube may be closed between both conductive parts, for instance, by heating and pinching it at this point.

Though in most cases said insulating bodies may consist of glass it is also possible to use other insulating materials, for example, magnesium oxide.

The invention will be more clearly understood by reference to the accompanying drawing, representing, by way of example, some forms of construction thereof.

Fig. l showsthe interior of a vacuum'tube according to the invention.

Fig. 2 is a plan view of this tube,

Figs. 3, 4, 5 and 6 are detail views of forms of construction of the invention, and;

Fig. 7 is a plan view at Fig. 6.

In Figs. 1 and 2 the glass wall or envelope I of the electron discharge tubeis provided with a stem 2 and a pinch 3. Through the pinch are led the supply conductors 4 and 5 for the heater element, the cathode lead-in conductor 6, the lead-in conductor I to the control grid and that 8 of the screening grid. The anode lead 811 is led in through the top of the envelope. Furthermore, the tube is furnished with an annular body 9 which by means of four supports I9 is fixed to the pinch. On this annular body is mounted the screening grid [0 (partly broken away for simplicity) andin addition the anode 20, whose supporting wires are connected to the said body by means of glassbeads so as to be insulated therefrom. The anode which may be made of nickel is shown in Figs. 1 and 2 as two rectangular plates 20, although it may assume other suitable constructions, such as a flattened cylinder.

On the pinch 3 there are mounted two supporting rods ll connected at the top by a cross bar I! carrying a supporting member l3 to which is fixed the cathode M, shown in the drawing as an indirectly heated cathode. Said supporting member serves at the same time for the current supply to the cathode body. Attached to the end of each supporting rod H and remote from the press is an insulating tubular member or bushing l5. Connected between these tubular members or bushings is the cross piece l5 which may be in the form of a metal strip and has the general contour shown in Fig. 2. The enlarged ends of the member 16 substantially surround and are embedded within circumferential depressions provided on the outer surface of each tubular member [5, while the upper ends of the supporting rods I? of the control grid 18 are clamped between opposite portions of the member H5 as indicated in Fig. 2.

By the use of said insulating bodies i5 which may consist, for instance, of glass and are connected together in the middle, the leakage path between the supporting rods I l and the conduc tive parts i5 is longer than that resulting from the use of glass beads of known construction. Moreover, in the present construction there is no risk of short circuits occurring over the surface of said insulating bodies on account of deposits of material, and in addition the conductive parts to go with the electrodes may expand freely without the risk of a breakdown of the glass insulators.

In Fig. 3 there is shown another form of construction wherein the insulating body designated by 2| consists of a solid portion 22 and two recessed portions 23. Two conductors 23' are arranged within the recessed portions and are secured to the insu ating body at 24. A third conductor 22 is sealed into the portion 22.

Fig. 4 shows another form of construction, in which the upper ends of the grid supporting rods '1' are slipped into two insulating bodies 26 which are closed at the top, a conductive part 21 being sunk into these bodies. By means of the fastening member 28 the part 2'! has fixed to it the cathode id, whereas the conductive parts 2'! are used at the same time for the supply of current to the cathode body.

In Fig. 5 the upper ends of the supporting rods I! are positioned within two insulating bodies 3| which are closed at top and around which is provided a conductive par 32 in form of a clasp. To this part is secured a fastening member 33 which has attached to it the cathode M in the same manner as illustrated in Fig. 4.

Figs. 6 and 7 show a form of construction in which three conductive parts are fixed to one insulating body. To this effect one of said tubular insulating bodies i5 is slipped over the end of each supporting rod 35 arising from the pinch of the discharge tube, the ends of rods extending within the insulators i5 but not penetrating to the middle thereof. To an intermediate part of each supporting rod 35 there is fixed a clasp or strap 3'! which supports the fastening member 38 attached to the cathode l4. Into the other ends of the insulators iii are inserted the conductive parts to which are secured the two cross members ll which in turn are fastened to the screening grid 42 through the rectangular end member 44. Finally fastening member 43 is attached to the insulating bodies 15, as in Figs. 1 and 2, opposite portions of said member having fixed between them the supporting rods I I of the control grid.

Though the drawing represents difierent forms of construction it will be understood that a great many modifications are possible without departing from the scope of the invention and by means of which it is also possible to yield the advantages resulting from the invention. It is possible, for instance, to secure a plurality of conductive parts to the outer side of the bodies referred to above, whereas said bodies may be given various shapes.

What is claimed is:

1. In an electron discharge tube, an evacuated envelope having a reentrant stem, anode, cathode and grid electrodes within the envelope, a pair of vertical support rods carried by the stem, a tubular insulating member mounted adjacent the end of each support rod remote from the stem, said support rods extending beyond the tubular members, a cross member joining the said extended ends of the support rods, a conductor connected between said cross member and the cathode, a pair of support rods for the grid electrode arranged close to the first mentioned support rods and also carried by the stem, and means carried by the tubular insulating members engaging the grid electrode supports.

2. In an electron discharge tube, an evacuated envelope having a reentrant stem, an electrode support rod extending above the stern and having one of its ends sealed therein, a laterally extending member rigidly secured to the opposite end of said support rod, a second support rod substantially coextensive with said electrode support rod and also having one of its ends sealed in said stem, and an insulating bushing slidably mounted on the opposite end of said second support rod and having a connection with said laterally extending member.

3. In an electron discharge tube, a press, a pair of spaced vertical support rods carried by the press with one of their ends sealed therein, means for insulatingly connecting togesher the other ends of said support rods which are remote from the press, comprising a tubular insulating member rigidly fixed to and carried by one of said support rods at that end remote from the press, the adjacent end of the other support rod arranged to slidably engage within the tubular insulating member.

4. In an electron discharge tube, a press, a plurality of spaced parallel support rods having one of their ends mounted in said press, means for insulatingly connecting together the other ends of said support rods, comprising a tubular insulating bushing loosely fitted over the last mentioned end of one of the support rods, and a connection between the adjacent end of the other support rod and the outer surface of the insulating member.

5. In an electron discharge tube, an evacuated envelope having a reentrant stem, anode, cathode and grid electrodes within the envelope, a pair of vertical support rods carried by the stem, a crossmember joined to the ends of the support rods remote from the stem, a conductor connected between said cross-member and the cathode, an insulating sleeve member slidably mounted upon each of the vertical support rods at that end adjacent to the cross-member, and a pair of grid electrode supports, each having one end fixed to the stem and the other end rigidly connected to one of the insulating sleeve members.

GREGORIUS J OHAN LAMBERT. JOHANNES WILLEM MEYJES. 

